The classification of pulmonary neuroendocrine neoplasms is particularly controversial. Large cell neuroendocrine carcinoma (LCNEC) has emerged as a separate entity among pulmonary endocrine neoplasms and the criteria for its histologic diagnosis are now well-described. However, cytologic diagnosis presents more difficulties and to the authors' knowledge, few cytologic studies concerning the entity have been published to date. The objective of the current study was to describe the cytologic features of LCNEC in an attempt to distinguish it from other pulmonary carcinomas.
A cytohistologic study of 11 surgical lobectomy specimens classified as LCNEC was performed. In all these cases, preoperative fine-needle aspiration cytology (FNAC) material was available for review.
The cytologic features of the cases were rather similar, resulting in a repetitive pattern. The majority of smears were hypercellular with numerous single, medium-to-large cells. Naked nuclei were abundant but a variable subset of cells demonstrated evident cytoplasm. Groups were 3-dimensional and of variable size, some of them large. Nuclear pleomorphism, molding, and mitosis were common findings. A necrotic background was evident in 6 cases. In 6 cases, neoplastic groups demonstrated peripheral nuclear palisading. Rosette-like structures were present in samples from 5 patients. In 4 cases, immunocytochemistry for the detection of synaptophysin was performed, with positive results.
The authors' experience with 11 FNAC cases of LCNEC, has led them to believe that the cytologic image of LCNEC is peculiar and recognizable in many cases. Nevertheless, it is a difficult diagnosis to make and immunocytochemistry plays a critical diagnostic role.